1. Field of the Invention
Oil gel compositions which have grease-like consistency at ambient temperature but which can be converted to have rubbery consistency by heating are formed by the combination of a grease-like gel in hydrocarbon oil and a grease-like gel in polar oil. The hydrocarbon oil gels are composed of styrenic diblock copolymers and mineral oil. The polar oil gels are composed of styrenic triblock copolymers in particular polar oils. The combinations of these two gels give the novel gels which have grease-like consistency at ambient temperature. When these two gels are combined in certain proportions and are heated, the styrenic triblock copolymer forms an elastic network, converting the gel from a grease-like consistency to a cohesive, rubbery gel. These cohesive oil gels can be formed upon demand by heating the final construction to a temperature around 120-150° C. and as such are referred to as “phase change” oil gels. These oil gels will be useful for a variety of applications including cable filling. In that particular application the oil gel will initially be easily pumpable, which is important in a cable filling operation. The gel will be controllably and locally solidified to make cutting and splicing operations cleaner and more efficient.
The present invention also comprises a method of making the oil gel composition and a method of making an optical fiber cable, as well as a fiber optic cable filled with the phase change oil gel.
2. Prior Art
In U.S. Pat. No. 5,900,455 discloses ground, neat polymer mixed with oil to make a paste that would fuse when heated.
U.S. Pat. No. 6,881,776 discloses two-phase gel compositions obtained by mixing a gelled ester composition comprising a mixture of: 1) an ester compound and a polymer compound selected from the group consisting of triblock copolymers, star polymers, radial polymers, multi-block copolymers, and a combination thereof, and 2) a hydrophobic, non polar solvent.
U.S. Pat. No. 7,994,256 discloses elastosols that can be handled as a paste at ambient temperatures, but which fuses at high temperature to become a cohesive, elastic composition. These compositions have utility as heat fusible sealants and caulks as well as elastomeric coatings. The solid rubbery gels are useful in a variety of applications, such as filling compounds for waterproofing copper cable and air fresheners. The solid rubbery gels have advantages over the prior art in that they can be prepared at ambient temperature, thereby simplifying the process for making and applying them.
U.S. Pat. No. 6,424,771 discloses a cable that includes a core comprising a plurality of coated optical fibers and a filling composition of matter that is disposed about the fibers. Typically, the fibers and the filling material are disposed within a tubular member that is disposed within a sheath system. The filling composition that fills interstices in the core is one that includes a mineral oil constituent that is a relatively high molecular weight aliphatic hydrocarbon. A relatively small percent by weight of a stereochemically hindered antioxidant system is used to prevent thermal oxidative degradation of the filling material. Such stereochemically hindered antioxidants will not migrate out of filling material into other cable and fiber materials, thereby increasing their effectiveness. A styrene-ethylene/propylene (S-EP) diblock copolymer is also included in order to reduce oil separation of the filling material. The diblock polymer and mineral oil form a gel that has grease-like consistency and therefore allows the optical fiber to move within the cable and yet if the cable is cut or breached, the gel repels any water.
U.S. Pat. No. 5,737,469 discloses a gel composition comprising a mineral oil and hydrogenated styrenic block copolymer that makes a gel for the optical fiber cable industry. Optional components are a thixotropic agent and an antioxidant.
The problem with optical fiber cables (FOC) comes when it is time to cut and splice them. Prior art gels having the consistency of grease are used in FOC to prevent ingress of water. They are made by thickening hydrocarbon oil with an S-EP diblock polymer. The grease-like consistency of the gel is an advantage in that it allows the fragile glass fibers to move within the sheath. However, it is a disadvantage if the cable needs to be repaired or spliced because the grease is difficult to remove from the fibers and coats every part of the cable and everything it comes in contact with like tools. It would be highly desirable to, on demand, convert the grease-like gel into a cohesive rubbery gel which could be easily stripped off the fibers yet stay in place. The present invention overcomes this problem with prior art gels.